Structuring spin domains in a BEC with spin-dependent light

We present our work on spatially structuring magnetic domains in multi-component Bose-Einstein condensates of $^{\mathrm{87}}$Rb, using spin-dependent optical potentials. For this, we make use of light at the tune-out wavelength (between the D1 and D2 line, for $^{\mathrm{87}}$Rb at 790.018 nm) to create optical barriers and potential wells sensitive to the hyperfine state of the atom. Using a focused Gaussian beam, and with appropriate circular polarization, this results in a repulsive barrier for (F,m$_{\mathrm{F}})=$(1,-1), and attractive well for the (1,$+$1) state, with the (1,0) state unaffected. We initially load a pure (1,-1) BEC into a flat-bottom line trap formed from a painted optical dipole potential. Using RF pulses, we drive spin transitions and prepare mixtures of (1,-1) with a tunable population of (1,0) or (1,$+$1) states. Using a 2D acousto-optical deflector, the spin-dependent light beam is steered and focused onto the BEC, resulting in localised repulsive barriers for the (1,-1) state. Through mean-field effects, the other hyperfine states fill in the resulting density dips in the (1,-1) condensate. Removing the light, we observe the formation of stable immiscible domains of (1,$+$1) embedded in the (1,-1) bulk.